The present invention relates to spectrophotometric analysis and is particularly concerned with apparatus for analysis of a sample material, typically in powder or liquid form, by reflectance measurements resulting from a beam of electromagnetic radiation (usually near infrared) applied to the material.
Spectrophotometers are well known to provide quantitive and qualitative analysis of substances and materials and are used extensively within the chemical, petro-chemical, food, agriculture and pharmaceutical industries. Typical infrared reflectance spectrophotometers are sold under the Trade Marks "COMPSCAN" by the Gardner Neotec Division of Pacific Scientific and "MODEL 6500" by NIR Systems Inc. Generally known reflectance spectrophotometers comprise a cell or container within which a sample of the material for analysis is retained; a source providing a beam of electromagnetic radiation (usually near infrared as previously mentioned) which is applied to the material in the cell, and sensors or detectors which are responsive to reflections from the material in the cell and provide an output from which the analysis is effected. Usually the spectrophotometer is coupled to a computer by which the application of the beam to the material is controlled and which provides a required analysis of the output from the sensors or detectors.
A particular concern when using reflectance spectrophotometers is to ensure that stray electromagnetic radiation reflected back to the sensors or detectors is minimised. Understandably such stray or spurious reflections from parts of the spectrophotometer apparatus to which the beam may be applied will be presented for analysis along with the intended reflections from the sample material and thus result in false or inaccurate measurements. Where relatively large volumes of material are available for spectrophotometric analysis so that such material may be presented in a sample cell or container distributed over a relatively large area which is subjected to the beam, the stray light reflectance may be regarded as insignificant in assessing the accuracy of the analysis measurements. However, when only a relatively small volume of sample material is available or desired for analysis there is a problem that spurious or stray light reflections can have a significant adverse effect on the accuracy of the analysis measurements--this problem frequently occurs in the pharmaceutical industry (where it is quite common for only a very small volume of highly expensive pharmaceutical to be made available for spectrophotometric analysis). It is an object of the present invention to provide an apparatus for reflectance spectrophotometric analysis by which the aforementioned problem may be alleviated. It is also an object of the present invention to provide an apparatus in the form of a conversion kit by which conventional reflectance spectrophotometers may be converted in a relatively simple, efficient and economic manner for use with a cell or container for a relatively small sample of material that is to be subjected to analysis and which conversion alleviates the aforementioned problem of stray or spurious reflections from the electromagnetic beam from being applied to the sensors or detectors.